Take-All disease is a serious problem in the production of cereals, particularly wheat and barley. It is caused by the soil-borne fungus Gaeumannomyces graminis var. tritici (Ggt). The fungus infects the roots of the plant, and grows throughout the root tissue, causing a black rot. The growth of the fungus in the roots and lower stem prevents the plant from obtaining sufficient water and/or nutrients from the soil, and is manifested as poor plant vigor and, in severe instances of disease, the formation of "whiteheads," which are barren or contain few, shriveled grains. Yield losses result. Gaeumannomyces graminis species also infect other cereal crops, for example, rice and oats, and turf.
Currently the primary means of avoiding crop loss due to infestation of the soil by Ggt has been to rotate the crop grown to one which is resistant to Ggt. In areas where the primary crops are cereals, however, rotation is not a desirable practice, and an effective control agent is greatly desired.
It is an object of this invention to provide an effective method for control of Take-All disease in plants. It is a further object of this invention to provide compounds that control the growth of Ggt in the soil so as to reduce crop loss. It is a still further object of this invention to provide fungicidal compositions that may be used for control of Take-All disease.
Control of Take-All disease has been the subject of a number of commonly assigned patents, including U.S. Pat. Nos. 5,482,974, 5,486,621, 5,693,667 and 5,705,513. Published foreign applications include EP 0538231 A1 and WO 95/24380.
This invention includes a new family of chemical compounds found effective for control of Take-All disease which are different from those disclosed in the previous patents and published applications, as will be seen in the description and Examples below.
International Publication No. WO 96/23763 is assigned to Bayer AG and relates to alkoximino acetic acid amides for use as fungicides. In some respects, the compounds are similar to those of the present invention. They differ in requiring ring compounds in the amide group, and in the preferred oxime geometry. More importantly, of the many fungal species mentioned in the application, there is no reference to the fungus responsible for Take-All disease, Ggt.